The long-term goal of this research is to explore the molecular mechanisms that bacteria use for cell-cell communication (i.e., quorum sensing). Until recently, the ability of bacteria to communicate was considered an anomaly that occurred only in a few marine Vibrio species. It is now clear that cell-cell communication is the norm in the bacterial world and that understanding this process is fundamental to all of microbiology, including industrial and clinical microbiology. Here we propose an integrative chemical biological study of the quorum-sensing circuit of the human pathogen Vibrio cholerae, the causative agent of the disease cholera. The V. cholerae quorum-sensing circuit depends on the production and detection of a small molecule signals called autoinducers. We propose to collaborate with the MLPCN to identify small molecules that modulate three distinct steps in the quorum-sensing cascade by performing an established high- throughput screen. Follow up secondary screens will define the modes-of-action of these lead compounds and categorize them as: 1. Quorum-sensing receptor agonists;2. LuxO inhibitors;3. Hfq inhibitors. Molecules identified through this work will provide new tools to probe the molecular mechanisms governing the quorum-sensing regulatory networks of V. cholerae and other microorganisms. Additionally, these compounds will be used as leads for the development of broad-spectrum antibacterial drugs designed to interfere with quorum sensing. Such therapies could have enormous ramifications for improving human health. PUBLIC HEALTH RELEVANCE: V. cholerae is a globally important pathogen that causes several million cases of disease per year. Our studies have shown that, in order to be pathogenic, V. cholerae must possess an intact quorum-sensing system because cell-cell communication controls the timing underlying production and release of virulence factors and the formation of biofilms. The investigations proposed here will facilitate the development of synthetic strategies for controlling quorum sensing in this important pathogenic microbe and possibly other pathogenic bacteria that use quorum sensing to control virulence.